Mass produced drive shafts for automobiles and other land vehicles have commonly been formed of steel thereby adding significant weight to the overall vehicle.
Additionally, it heretofore has been recognized that vehicles (particularly those with four cylinder engines) sometimes encounter undesirable powertrain noise, e.g. when the engine rotates between 3500 and 5000 RPM. This noise commonly is called "boom". Two techniques have commonly been employed in the automotive industry to solve the "boom" phenomenon. The most popular approach is to replace the one piece steel shaft with a two piece shaft having a center universal thereby increasing the complexity of the driveline. The second approach is to attach mass balance weights to certain points of the driveline, e.g. the transmission extension housing. Each solution adds further weight to the vehicle and increases the cost of production. Additionally, when the former approach is pursued additional maintenance expense may result should the center universal joint require servicing.
Fiber reinforced composite drive shafts have been proposed in the past for use with helicopters and in automotive applications. Such drive shafts have held out the hope of possibly reducing the overall weight of the vehicle. For instance, early composite drive shafts proposed for automotive usage were composed of glass fibers embedded in a resinous matrix (e.g. a thermoset resin). These shafts were found to suffer from lack of stiffness and also exhibited poor fatique characteristics which prevented their commercial application.
More recently, fiber reinforced drive shafts comprising both glass fibers and carbon fibers in a resinous matrix have been disclosed. See published Japanese Application No. 52-127542 entitled "Carbon Fiber Drive Shaft" which claims priority for the filing of U.S. Ser. No. 676,856 on Apr. 14, 1976 by Gordon Peter Worgan and Derek Reginald Smith (now U.S. Pat. No. 4,089,190). See also U.S. Pat. No. 4,041,599 to Derek Reginald Smith which makes passing reference to a carbon fiber reinforced epoxy drive shaft. The former disclosure indicates that a carbon fiber reinforced composite drive shaft or a carbon fiber and glass fiber reinforced composite drive shaft of a specific structural configuration having a maximum longitudinal composite modulus of elasticity of 8 million psi and preferably less than 6 million psi is successful in reducing the noise generated by one piece steel drive shafts and successfully enables the elimination of intermediate universal joints which are commonly employed to reduce powertrain noise in automobiles.
It has been found, however, that the fiber reinforced composite drive shaft proposed in published Japanese Application No. 52-127542 does not provide a solution to "boom" problem experienced in drive shafts of many current automobiles. Accordingly, experimental efforts have continued in seeking to design a reliable fiber reinforced composite drive shaft which is free of undesirable noise generation. Additionally, the cost of carbon fibers has heretofore militated against their utilization as fibrous reinforcement in large quantities in cost critical applications such as drive shafts.
It is an object of the present invention to provide a fiber reinforced composite drive shaft of reduced weight which can be substituted for a steel drive shaft heretofore utilized without loss of service characteristics or the requirement that a costly two piece shaft with a center universal be employed.
It is an object of the present invention to provide a carbon fiber reinforced composite drive shaft which successfully overcomes the noise problem found to be associated with that disclosed in published Japanese Application No. 52-127542.
It is an object of the present invention to provide a fiber reinforced composite drive shaft which requires minimal utilization of relatively more costly carbon fibers without sacrifice of desirable performance characteristics.
It is another object of the present invention to provide an improved light weight carbon fiber reinforced composite drive shaft which can be manufactured on a cost competitive basis compared to conventional steel drive shafts.
These and other objects, as well as the scope, nature, and utilization of the invention will be apparent to those skilled in the art from the following detailed description and appended claims.